Polycarbonate has found many uses as a class of materials because it combines, in general, a high level of heat and impact resistance, good dimensional stability, and good insulating and non-corrosive properties. For example, halogenated polycarbonate (and copolycarbonate) are known especially for resistance to physical deformation at high temperature and resistance to flammability.
In the performance of various known interfacial processes for preparing halogenated polycarbonate, it is found that the reaction mixture is thoroughly emulsified by the time formation of the polycarbonate product is complete, and several hours are required for the organic phase to separate from the emulsified mixture. It is difficult to readily wash an emulsified product-containing solution thoroughly enough to remove foreign material such as catalysts or inorganic salts, and the performance in a service environment of a product containing such foreign material is frequently impaired.
It is also found that certain of these known processes for preparing halogenated polycarbonate yield a product which is shown by analysis to contain significant amounts of Phenolic End Groups (a Phenolic End Group being an --OH moiety at a polycarbonate chain end); and/or Process Chemical End Groups (a Process Chemical End Group being the residue yielded at a polycarbonate chain end by reaction with the polycarbonate chain of a process chemical, such as a catalyst or other chemical which promotes, directs, regulates or otherwise influences the progress of the polycarbonate forming reaction). Analysis also reveals that halogenated polycarbonate containing significant amounts of Phenolic and/or Process Chemical End Groups is characterized by a tendency toward thermal degradation, as evidenced by the formation of color bodies upon heating.
It would consequently be desirable to provide a process for preparing halogenated polycarbonate which is improved over known processes such as are described above.